Lubricating oil compositions



United States Patent 18 Claims. (CL 252-5) This invention relates to lubricants, particularly those suitable for lubrication under severe operating conditions,

such as under extreme high speed and at high temperatures.

It is well known that the high pressure occurring in certain types of gears and bearings may cause rupture of lubricant films with consequent damage to the machinery. It has been shown that various base lubricants can be improved in their protective properties for rubbing surfaces by the addition of certain substances, socalled extreme pressure agents, so that excessive wear, scutfing and seizure which normally follow a break in the film lubricant, can be minimized or prevented.

It is known that certain compounds of metal-reactive elements, such as certain compounds of chlorine, sulfur and phosphorus, as well as certain other compounds, such as some compounds of lead, impart extreme pressure properties to various lubricants. Notable among the substances heretofore used are the lead soaps, phosphoric acid esters, free or bound sulfur and certain chlorinated organic compounds. A principal objection to many of these extreme pressure agents is their generally high reactivity with the metallic surface, causing etching, corrosion and discoloration of the metal surface. Another objection to chemically reactive extreme pressure agents is that they alter the original chemical nature of the contacting surface, which under certain conditions is undesirable. Additionally, because of the activity of agents of this type, they usually are depleted rapidly resulting in only a temporary solution to the problem of extreme pressure lubrication.

It has now been discovered that improved extreme pressure lubricants are provided by a suitable lubricating oil containing certain marginally oil-soluble aliphatic dicarboxylic acids. The aliphatic dicarboxylic acids have the formula HOOCC H R COOH, wherein R is an alkyl radical of from 1 to 4 carbon atoms, n is an integer of from 3 to 6, m is an integer of from 1 to 6 inclusive, and the total number of carbonatoms in all Rs is from 1 to 6. The dibasic acids are C -alkyl substituted glutaric, adipic, pimelic or suberic acids, wherein the two acid groups are separated by a chain of from 3 to 6 carbon atoms. One or more of the connecting carbon atoms is substituted with alkyl, preferably methyl, radicals to a total of from 1 to 6 carbon atoms in all alkyl radicals in a given molecule, preferably no more than three.

The acid groups must be separated by a chain of three to six carbon atoms to provide the superior extreme pressure properties and in addition the separating alkylene radical --C (H- R must contain at least one side-chain alkyl radical (R) in order to provide the minimum required oil solubility while not unduly adversely affecting the extreme pressure properties of the dibasic acid. Dibasic acids in which the acid groups are separated by less than three carbon atoms, such as succinic acid, or by more than six carbon atoms, such as sebasic acid, have been found to be poor extreme pressure agents,

2,971,915 Patented Feb. 14, 1961 even when one or more of the connecting carbon atoms is substituted with an alkyl radical of from 1 to 6 or more carbon atoms. r

The useful dibasic acids in general are marginally oilsoluble. However, they should be soluble in oil to the extent of at least about 0.5% by weight, better at least 1% by weight, but not over about 10% by weight and preferably not over about 5% by weight. The solubility of the acids in the oil can be increased by providing oilsoluble branched-chain aliphatic alcohols, in the oil as a solubilizing agent. These alcohols efiectively solubilize the dibasic acids of lower oil-solubility while the acids retain their extreme pressure properties in the oil.

More specifically, the dibasic acids are represented by such substances as the 2-; 2,2-, 2,3-, 3-, 3,3-, 4-, 4,4-, 2,4-, 2,5-, 2,3,4-, 2,3,5-, mono, di, and tri, methyl or ethyl or 2-, or 3-, monobutyl glutaric adipic, pimelic or suberic r 1C3 I acids. Preferred acids are 2-methyl glutaric acid, 2- 'methyl adipic acid, Z-methyl pimelic acid, Z-methyl suberic acid, 3-methyl glutaric acid, 3-methyl adipic acid, 3-methyl pimelic acid, 3-methyl suberic acid, 2,2-dimethyl glutaric acid, 2,2-dimethyl adipic acid, 2,3-dimethyl glutaric acid, 2,3-dimethyl adipic acid, 3,3-dimethyl adipic acid, 2,4-dimethyl adipic acid, 2,2,4-trimethyl adipic acid, 2,3,4-trimethyl adipic acid, 2,2,4-trimethyl suberic acid, 3-ethyl glutaric acid, 2-methyl, 3-ethyl adipic acid, 2- methyl-4-butyl suberic acid and mixturesthereof.

These extreme pressure agents are miscible in mineral lubricating oils at room or storage temperatures up to about 2% by weight. When it is desired to incorporate an amount of dibasic acid in the oil in excess of its oilsolubility at room temperature, a branched-chain alkanol is useful. These alkanols efiectively solubilize the dibasic acids so that amounts of as high as 10% by weight, basedflon the total oil compositions, can be dispersed in the o' Particularly useful alkanols for the purpose of solubilizing the dibasic acids, without interfering with their extreme pressure activity, are the so-called 0x0 alcohols derived from branched-chain olefin's, such as polymers of lower-alkenes of 3 to 5 carbon atoms, and copolymers of mixtures of such alkenes by catalyzed reaction with car bon monoxide and hydrogen in accordance with the conditions of the0xo process, as is well known in the art. The composition of a typical C -oxo-alcohol mixture derived from' a mixture of C olefins, produced by polymerization of a typical refinery cracked gas fraction of C -C hydrocarbons,- is given in Table I.

TABLE I Alcohol Percent, wt.

3,5-dl'nethyl hexa 29 t s-dlmethvl hexanol 25 3,4-dlnethvl herannl 17 B-methvl heptanol 3. m hnptnnnl 16 b-ethyl horannl 2. 3 6,5-di'nethvl haxanol 1. 4 aalkyl alk h 4. 3 other! 5. 0

Other examples of suitable alkanols include 6-methyl-lheptanol, 2-n-propyl-l-pentanol, 3-n-propyl-l-hexanol, 2,2-dimethyl-l-octanol, 10,10-dimethyl-l-undecanol, 3- isopropyl-l-hepanol and mixtures thereof.

The lubricating oils used in compositions of this invention can be a variety of synthetic or natural hydrocarbon oils having a viscosity range of from 5W SUS at 100" F. to 250 SUS at 210 F. (SAE viscosity number ranging from SAE 50 to SAE The natural hydrocarbon oils can be obtained from parafiinie, naphthenic, asphaltic or mixed base crudes, and/or mixtures thereof.

3 Synthetic oils include polymerized olefins, alkylated aromatics, isomerized waxes, copolymers of alkylene glycols and alkyleneoxide (Ucon fluids) which are described in US. Patents 2,425755, 2,425,845 and 2,774,733 such as Ucon 50HB170, Ucon 50HB660 or Ucon LB550X and which are copolymers of ethylene and 1,2-propylene oxides the mono and diols as well as their ether derivatives; organic esters of an aliphtic dibasic acid such as di-Z-ethyl hexyl sebacate or di-Z-ethyl hexyl adipate and the like. The hydrocarbon oils may be blended with fixed oils such as castor oil, lard oil and the like and/or synthetic oils as mentioned or silicone polymers and the like. Typical oils of this type are petroleum motor oils (A) which is I paraflinic in character and (B) which is naphthenic in character having the following properties:

(SA 10W) (BAE 30) F -10 -5 1 i: 390 41s Viscosity, BUS at 210 F 44 58 Viscosity Index 90 G) Other suitable oils are the gas turbine lube oils having the following properties:

Grade 1010 1065 Flash, 000, F 300 Pour, F 10 Viscosity, SUS at 100 F- 59.4 Neutral Number 0. 02 0. 01 Ash None None Compositions A through 0 are representative of invention wherein the base oils are identified hereinabove Composition C:

garners Composition K. Percent wt. S-methyl adipic acid 2 Mineral oil (8) Balance Composition L:

3-ethyl adipic acid 2 C Oxo alcohol 3 Mineral oil (B) Balance Composition M:

2,3-dimethyl adipic acid 2 Ucon 501-18660 Balance Composition N:

2,3-dimethyl adipic acid 2 Ucon LB-SSOX Balance Composition 0:

2.3-dimethyl adipic acid 2 Di-2ethyl hexyl sebacate Balance Speed p m-- 3200 Oil temperature F... 100 Oil flow-rate cc./scc 10 Load in increments 5 min. at each setting.

Results of the evaluations are given in Table II; For purpose of comparison, the results obtained from the use of the base oil alone, and with other dicarboxylic acids, are also given in Table II.

TABLE II Spur gear machine test results Oompodtion 2,2-dimethyl glutaric acid 2 1010 mineral oil a ce Composition D:

3-methyl adipic acid 2 1010 mineral oil Balance Composition E: 1

2,4-dimethyl adipic acid 2 1.010 mineral .oil 3118 60 Composition/F:

2,2,4-trimethyl adipic acid 2 i358 1010 mineral oil Balance s m iner l 11am Composition ii'i 2-methyl pimelic acid 2 1010mm"! 600 C 0x0 alcohol 3 1010 mineral oil Balance thl'hus, the data show the outstanding enhancement of e load-carrying ability of the oil effected by the digf gggg acid 2 carboxylic acids of the invention, as represented by 1010 mineral oil Balance those of COmPOSIUOIIS A through 0. On the other hand,

r I malonic acid and succinic acid in which the two car- Composition 1: boxylic acid groups are separated by only one and two S-methyl glutaric acid 3 Carbon atoms, respectively, and C -alkenyl succinic acid C 0 l h l 3 in which oil-solubility is obtained by the C -hydrocar- 1010 mineral oil Balance bOn radical effected only a slight improvement. Also whereas 3-methyl adipic acid (Composition D) in- Composition I creased the load capacity from 600 to 10,000 pounds per 3-methyl glutarrc acid 3 square inch, the higher alkyl-homolog, 3-hexadecyladipic C Oxo alcohol 3 acid, gave an increase of only 800 from 600 to 1400 2,6-ditert butyl-4 methyl phenol 0.1 pounds per square inch. 1010 mineral oil Balance (a The dicarboxylic acids of this invention are useful also for providing superior load carrying properties in lubricating oils which contain minor amounts of other agents which are non-reactive with the dicarboxylic acids, such as silicone anti-foaming agents, alkylphenol antioxidants, polyacrylate ester viscosity-index improvers, and the like.

We claim as our invention:

1. A lubricating oil composition comprising a major amount of lubricating oil and from about 0.1% to about 2% of an aliphatic dicarboxylic acid having the formula HOOCC H R COOH wherein R in the side chain of the hydrocarbon group C I-l ll and is an alkyl radical of from 1 to 4 carbon atoms, )1 is an integer of from 3 to 6, m is an integer of from 1 to 6 inclusive and the total number of carbon atoms in all Rs is from 1 to 6.

2. The lubricating composition of claim 1 wherein the lubricating oil is a mineral lubricating oil.

3. The lubricating composition of claim 1 wherein the lubricating oil is selected from the group consisting of a polyoxy alkylene diol and the mono and diethcrs thereof.

4. The lubricating composition of claim 1 wherein the lubricating oil is an organic ester of an aliphatic dibasic acid.

5. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1% to about 2% of C -C alkyl substituted glutaric acid.

6. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1 to about 2% of a C -C alkyl substituted pimelic acid.

7. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1% to about 2% of a C -C alkyl substituted adipic acid.

8. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1% to about 2% of a C -C alkyl substituted suberic acid.

9. A lubricating composition comprising a major 6 amount of a mineral lubricating oil and from about 0.1% to about 2% of B-methyl glutaric acid.

10. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1% to about 2% of 3,3-dimethyl glutaric acid.

11. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1% to about 2% of S-methyl adipic acid.

12. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1% to about 2% of 2,3-dimethyl adipic acid.

13. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1% to about 2% of 2-methyl pimelic acid.

14. The lubricating composition of claim 9 containing a minor amount of a branched-chain alkanol.

15. The lubricating composition of claim 10 containing a minor amount of a branched-chain alkanol.

16. The lubricating composition of claim 11 containing a minor amount of a branched-chain alkanol.

17. The lubricating composition of claim 12 containing a minor amount of a branched-chain alkanol.

18. The lubricating composition of claim 13 containing therein a minor amount of a branched-chain alkanol.

References Cited in the file of this patent UNITED STATES PATENTS 2,133,734 Moser Oct. 18, 1938 2,158,096 Werntz May 16, 1939 2,334,158 Von Fuchs Nov. 9, 1943 2,402,825 Lovell et al June 25, 1946 2,452,319 Patterson et a1 Oct. 26, 1948 2,452,320 Kluge et a1. Oct. 26, 1948 2,459,717 Perry Jan. 18, 1949 2,548,493 Robey Apr. 10, 1951 2,788,326 Bondi et a1 Apr. 9, 1957 

1. A LUBRICATING OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF LUBRICATING OIL AND FROM ABOUT 0.1% TO ABOUT 2% OF AN ALIPHATIC DICARBOXYLIC ACID HAVING THE FORMULA HOOCCNH2N-MRMCOOH WHEREIN R IN THE SIDE CHAIN OF THE HYDROCARBON GROUP CNH2N-MRM AND IS AN ALKYL RADICAL OF FROM 1 TO 4 CARBON ATOMS, N IS AN INTEGER OF FROM 3 TO 6, M IS AN INTEGER OF FROM 1 TO 6 INCLUSIVE AND THE TOTAL NUMBER OF CARBON ATOMS IN ALL R''S IS FROM 1 TO
 6. 